More IBA-Recycling in Germany in 2024

The recovery of incineration bottom ash (IBA) in technical structures rose further in Germany in 2024. After approximately 13 per cent in 2022, the share reached around 25 per cent in 2024. The previous negative trend in this disposal route has thus been halted. These findings come from the fourth joint trade association survey conducted by ITAD (Interessengemeinschaft der Thermischen Abfallbehandlungsanlagen in Deutschland) and the Bundesverband Mineralische Kreislaufwirtschaft und nachhaltige Entsorgung (BMKE, formerly IGAM).

Despite this increase, landfill recovery and disposal combined continue to account for over 70 per cent of all disposal routes for IBA, making it by far the largest route. For the first time, the associations have also calculated the contribution of metal recovery from the ash to climate protection: the savings potential amounts to approximately 1.04 to 1.57 million tonnes of CO2 equivalents per year.

Data Basis: 39 Plants for Reporting Year 2024

For the data monitoring exercise, ITAD and BMKE surveyed members and non-members between July and December 2025 using a sector-specific questionnaire for the 2024 reporting year. All 39 operators of slag processing plants in Germany known to the associations participated. The survey covered key data on mineral material flows as well as metals recovered from the processing of bottom ash produced during the thermal treatment of municipal and commercial waste at Waste-to-Energy plants with grate firing.

ITAD member plants account for approximately 96 per cent of Germany’s treatment capacity. According to their data, the average fresh slag share from grate firing in 2024 was around 24.6 per cent of the waste delivered, equivalent to approximately 5.94 million tonnes of fresh slag from around 24.15 million tonnes of waste. Including capacities not covered by ITAD, the extrapolated fresh slag volume in Germany amounts to up to 6 million tonnes.

Mass Balance: 5.665 Million Tonnes of Raw Slag

Prior to processing, approximately 25,000 tonnes of coarse metal scrap were separated, of which around 21,000 tonnes were recoverable, assuming a metal yield of approximately 85 per cent. After deducting further differences in stock levels, water losses, and other losses of up to 310,000 tonnes, this resulted in 5,665,000 tonnes of raw slag for processing.

Within this raw slag, 84,000 tonnes (1.48 per cent) consisted of unburned material and a further 361,000 tonnes (6.39 per cent) of water losses and stock differences during processing. Processing yielded 415,000 tonnes of ferrous metal scrap (7.33 per cent of raw slag) and 173,000 tonnes of non-ferrous metal scrap (3.05 per cent). The processed slag amounted to 4,632,000 tonnes, representing 81.77 per cent of raw slag.

Metal Recovery Slightly Increased Since 2017

Of the 415,000 tonnes of ferrous metal scrap, 373,000 tonnes (6.58 per cent of raw slag) were recoverable; of the 173,000 tonnes of non-ferrous metal scrap, 86,000 tonnes (1.52 per cent) were recoverable. Including the coarse metal scrap separated prior to processing, the total separated metal scrap came to 613,000 tonnes (10.82 per cent), of which 480,000 tonnes or 8.47 per cent were recoverable. The average weighted iron content in the ferrous metal scrap was above 89 per cent; the average metal yield from non-ferrous scrap was around 50 per cent.

Comparing the years 2017, 2020, 2022, and 2024, the share of all separated metal scrap in raw slag increased slightly from 9.94 per cent via 10.64 and 10.28 to 10.82 per cent. The share of recoverable metals ranged between 8.07 and 8.53 per cent during this period, reaching 8.47 per cent in 2024.

Metal Recycling Saves up to 1.57 Million Tonnes of CO2

IBA represents a reliable raw material potential for the production of metal scrap, explained Ragnar Warnecke, Chairman of ITAD. Metal recycling, he said, remains at a high level as in previous years and avoids emissions that would arise from the production of metals using primary raw materials.

According to the associations’ calculations, the recovery of recoverable metals yields savings potential of approximately 1.04 to 1.57 million tonnes of CO2 equivalents per year. The recoverable ferrous metals alone (394,000 tonnes) contribute 594,940 to 689,500 tonnes of CO2. For non-ferrous metals (86,000 tonnes), the aluminium share (approximately 60,200 tonnes, around 70 per cent) accounts for 410,793 to 757,316 tonnes of CO2, whilst the copper share (approximately 25,800 tonnes, around 30 per cent) accounts for 34,830 to 122,808 tonnes of CO2.

With regard to the mineral fraction, the association is working together with other trade bodies to open up new fields of application in which bottom ash can be used to produce secondary construction materials. The forthcoming Roadmap 2045 shows that the resource potential from bottom ash will remain at a similar level for the foreseeable future. The associations are calling on legislators to create appropriate frameworks, based on the findings of numerous research projects, in order to unlock this potential.

Carbonation Calculated for the First Time

For the first time, the associations also calculated how much CO2 the slag additionally binds from the atmosphere through natural carbonation. Studies indicate that static carbonation processes bind between 15 and 33 kilogrammes of CO2 per tonne of raw slag. Based on an assumed average of 23 kilogrammes per tonne, the approximately 6 million tonnes of raw slag generated in 2024 resulted in an additional CO2 binding of 138,000 tonnes.

Recovery in Structures: Negative Trend Halted

The multi-year comparison reveals a turnaround in recovery in technical structures: after 857,000 tonnes (18.1 per cent) in 2017, the volume fell to 699,000 tonnes (14.9 per cent) in 2020 and 603,000 tonnes (13.1 per cent) in 2022, before rising to 1,157,000 tonnes (25.0 per cent) in 2024.

For the other disposal routes, the 2024 survey produced the following figures: landfill recovery 2,388,000 tonnes (51.6 per cent), landfill disposal 868,000 tonnes (18.7 per cent), and underground recovery in mining 219,000 tonnes (4.7 per cent). Other recovery routes, still used for 102,000 tonnes (2.2 per cent) in 2022, were no longer used in 2024. The total processed slag volume in 2024 stood at 4,632,000 tonnes, compared with 4,592,000 tonnes (2022), 4,688,000 tonnes (2020), and 4,731,000 tonnes (2017).

Material Class HMVA-2 Dominates Under New Regulation

A key driver of the joint survey was once again the promotion of the recovery of household waste incineration ash in technical structures in the context of the German Substitute Building Materials Ordinance (Ersatzbaustoffverordnung). For the first time, the associations also surveyed how the ash recovered under this regulation is used: according to the companies surveyed, 100 per cent consisted of material class HMVA-2.

This material is used primarily as a frost protection layer (installation method 8) and for backfilling building excavations and utility trenches under a bound surface layer (installation method 4). To a lesser extent, it is used as a sub-base under foundation or floor slabs (installation method 2) and in embankments or levees (installation method 9).

Public Sector Holding Back Recycling Trend

The 2024 figures show that the recovery of household waste incineration ash in technical structures has increased under the Substitute Building Materials Ordinance, explained Rebecca Winkler, Chair of the IBA Working Group and Deputy Chair of the Bundesverband Mineralische Kreislaufwirtschaft und nachhaltige Entsorgung. Increased demand from private users in particular can be observed, she said.

This trend cannot, however, be observed amongst public-sector clients. The obligations of public authorities to give preference to recycled materials therefore need to be tightened. The consistently high level of landfill recovery and disposal demonstrates the considerable potential for higher-grade recovery of IBA in Germany.

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